Ontogeny of estrogen receptor-β expression in rat testis

The recently discovered estrogen receptor-β (ERβ) is expressed in rodent and human testes. To obtain insight in the physiological role of ERβ we have investigated the cell type-specific expression pattern of ERβ messenger RNA (mRNA) and protein in the testis of rats of various ages by in situ hybridization and immunohistochemistry. In fetal testes of rats 16 days postcoitum and testes of 4-day-old animals, fetal germ cells (gonocytes) reveal the ERβ mRNA in their cytoplasm and the ERβ protein in their nucleus. In testes of 11- and 15-day-old rats, ERβ mRNA and protein were detected in Sertoli cells and type A spermatogonia. No signal was found in other types of germ cells. In the adult testes, expression of ERβ mRNA as well as ERβ protein was found in pachytene spermatocytes from epithelial stages VII-XIV and in round spermatids from stages I-VIII. Low ERβ expression was observed in all type A spermatogonia, including undifferentiated A spermatogonia, whereas no expression was found in In and type B spermatogonia and early spermatocytes. At all ages, Sertoli cells showed a weak hybridization signal as well as weak immunoreactivity for ERβ. In adult testes, no ERβ mRNA or protein was detected in the interstitial tissue, indicating that Leydig cells and peritubular myoid cells do not express ERβ. The expression of ERβ in fetal and late male germ cells as well as in Sertoli cells suggests that estrogens directly affect germ cells during testicular development and spermatogenesis.